1. Field of the Invention
The present invention relates to a vertical takeoff and landing aircraft or a short takeoff and landing aircraft (hereinafter referred to as a V/STOL aircraft as well) and to a torque transmission. The present invention may be favorably applied to an aircraft which uses bi-blade rotors and bi-blade variable pitch propellers.
2. Description of the Prior Art
(a) As regards prior art V/STOL aircraft, prototypes of a number of tilt rotor aircraft have been manufactured since the 1950s. Typically, in the case of such an aircraft, wings equipped with propellers and engines is tilted with respect to the fuselage, or propellers equipped with engines are tilted, to direct the thrust upward, thereby performing vertical takeoff and landing similarly to helicopters. In the case of a prior art tilt rotor aircraft as mentioned above, flight is performed such that propellers equipped with engines are turned upward when a vertical takeoff or a vertical landing is made (in the helicopter mode) and propellers equipped with engines are turned forward when a level flight is made (in the fixed aircraft mode). The time required for the transition from the helicopter mode to the fixed wing mode or the other way around is more than ten-odd seconds, thus causing a problem in that the aircraft becomes very unstable during the transition.
(b) Prior art torque transmissions for VTOL aircraft serve to transmit engine output to propellers or rotors, but do not serve to transmit engine output simultaneously to propellers and rotors.
Propellers and rotors are prerequisites for realizing a VTOL aircraft capable of safely and easily switching from the helicopter mode to the fixed wing mode, as well as from the fixed wing mode to the helicopter mode.
For this purpose, it is necessary to have a simple torque transmission capable of transmitting engine output simultaneously to propellers and rotors. However, prior art torque transmissions cannot transmit engine output simultaneously to propellers and rotors.
(a) xe2x80x9cHelicopter modexe2x80x9d
The helicopter mode is defined as a flight mode wherein an aircraft stays aloft by means of only the lift of rotors (i.e. the resultant of the lifts produced by rotors), with the lift of fixed wings equal to zero.
(b) xe2x80x9cFixed wing modexe2x80x9d
The fixed wing mode is defined as a flight mode wherein an aircraft flies by means of only the lift produced by fixed wings, with the lift of rotors equal to zero.
(c) xe2x80x9cCompound modexe2x80x9d
The compound mode is defined as a flight mode wherein an aircraft flies by using the lift produced by rotors and the lift produced by fixed wings.
(d) xe2x80x9cRotor and rotor liftxe2x80x9d
A rotor is defined as a member comprising:
a plurality of rotor blades producing a lift during rotation;
a rotor shaft supporting the above-mentioned rotor blades; and
a rotor lift is defined as the resultant of the lifts produced by a plurality of rotor blades.
The object of the present invention is, in view of the above-mentioned circumstances, to provide an aircraft and a torque transmission which are capable of resolving the problems stated in items (a) through (d) below.
(a) An aircraft which is capable of flying in the compound mode, wherein rotors and fixed wings produce a lift, in the helicopter mode, wherein only rotors produces a lift, and in the fixed wing mode, wherein only fixed wings produce a lift, shall be provided.
(b) An aircraft which has satisfactory stability and controllability both in the helicopter mode and in the fixed wing mode shall be provided.
(c) An aircraft which does not become unstable during transition either from the helicopter mode to the fixed wing mode or from the fixed wing mode to the helicopter mode shall be provided.
(d) A torque transmission, a bi-blade rotor, and a bi-blade propeller all of which may be favorably used on the above-mentioned aircraft shall be provided.
In the next place, the present invention, which was devised for the purpose of resolving the above-mentioned problems, is explained.
For the purpose of resolving the above-mentioned problems, an aircraft of the first aspect of the present invention comprises:
1. An aircraft comprising:
(a) an airframe having,
(1) a fuselage extending longitudinally,
(2) a set of fixed wings consisting of a main wing and a horizontal tail wing both of which are connected to the above mentioned fuselage at two locations longitudinally apart from each other and both of which extend laterally and are capable of producing lifts during forward flight, and a vertical tail wing,
(3) two ailerons one of which is installed on the right-hand section of the above mentioned main wing and the rest of which is installed in the left-hand section of the above mentioned main wing,
(4) two elevators one of which is installed on the right-hand section of the above mentioned horizontal tail wing and the rest of which is installed in the left-hand section of the above mentioned horizontal tail wing, and
(5) a rudder installed on the above mentioned vertical tail wing;
(b) a propeller-rotor torque transmission having,
(1) a shaft support coupler wherein
one end each of a propeller shaft support and a rotor shaft support both of which lie at right angles to each other,
and one end of an input shaft which lies at right angles to the above mentioned propeller shaft support and to the above mentioned rotor shaft support or which lies coaxially with either the above mentioned propeller shaft support or with the above mentioned rotor shaft support,
are coupled together in such a way as to preclude rotation,
(2) a cylindrical input shaft which is installed in such a way as to permit rotation around the above mentioned input shaft support,
(3) a cylindrical propeller shaft which is installed in such a way as to permit rotation around the above mentioned propeller shaft support and on which a variable pitch propeller for producing a propelling force is installed,
(4) a cylindrical rotor shaft which is installed in such a way as to permit rotation around the above mentioned rotor shaft support and on which is installed a rotor head that supports a rotor blade for producing a lift such that only the collective pitch is variable, and
(5) a bevel gear which transmits the rotation of the above mentioned cylindrical input shaft (hereinafter referred to as an input shaft), simultaneously to the above mentioned cylindrical propeller shaft (hereinafter referred to as a propeller shaft), and to the above mentioned cylindrical rotor shaft (hereinafter referred to as a rotor shaft):
(c) an engine gearbox which supplies the above mentioned input shaft with rotational motive power; and
(d) a flight control system having,
(1) a propeller collective pitch controller which controls the pitch angle of the above mentioned variable pitch propeller;
(2) a rotor collective pitch controller which controls the collective pitch of the above mentioned rotor blade;
(3) an engine power controller which controls the output of the above mentioned engine gearbox for the purpose of changing the rotational speed of the above mentioned input shaft; and
(4) a directional (yaw) control system which controls the deflection angles of the above mentioned ailerons and the above mentioned rudder to control the flight direction of the aircraft during forward flight.
The aircraft of the present invention may be provided with a plurality of propeller-rotor torque transmissions.
Namely, only one propeller-rotor torque transmission may be installed on the aircraft, for example, in the upper central section of the aircraft;
a total of two propeller-rotor torque transmissions may be installed on the aircraft, for example, one in the right-hand section of the aircraft and the other in the left-hand section of the aircraft;
a total of three propeller-rotor torque transmissions may be installed on the aircraft, for example, one in the right-hand section of the aircraft, another in the left-hand section of the aircraft, and a third at a location forward or aft of the above-mentioned right-hand and left-hand propeller-rotor torque transmissions; or
a total of four propeller-rotor torque transmissions may be installed on the aircraft, for example, one in the right-hand section of the aircraft, another in the left-hand section of the aircraft, a third at a location forward of the above-mentioned right-hand and left-hand propeller-rotor torque transmissions, and a fourth at a location aft of the above-mentioned right-hand and left-hand propeller-rotor torque transmissions.
In a case where
one propeller-rotor torque transmission is located in the right-hand section of an aircraft, and another propeller-rotor torque transmission is located in the left-hand section of the aircraft: each of the above-mentioned right-hand and left-hand propeller-rotor torque transmissions is referred to as a main propeller-rotor torque transmission;
a propeller rotated by a main propeller-rotor torque transmission is referred to as a main propeller; and a rotor rotated by a main propeller-rotor torque transmission is referred to as a main rotor.
In a case where
a third propeller-rotor torque transmission is located at a position aft of the above-mentioned right-hand and left-hand propeller-rotor torque transmissions:
the above-mentioned aft propeller-rotor torque transmissions is referred to as a tail propeller-rotor torque transmission;
a propeller rotated by a tail propeller-rotor torque transmission is referred to as a tail propeller; and
a rotor rotated by a tail propeller-rotor torque transmission is referred to as a tail rotor.
In a case where
a main propeller-rotor torque transmissions is located in the right-hand section of the aircraft,
another main propeller-rotor torque transmissions is located in the left-hand section of the aircraft, and
a tail propeller-rotor torque transmission is located at a position aft of the above-mentioned two main propeller-rotor torque transmissions; the above-mentioned tail propeller-rotor torque transmission may be provided either with only a tail rotor for controlling the pitching of the aircraft or with only a tail propeller for performing directional (yaw) control of the aircraft.
It is possible to provide a plurality of engine gearboxes. For example, it is possible to realize a design such that two engine gearboxes are provided, one of which transmits rotation to two main propeller-rotor torque transmissions and the rest of which transmits rotation to two tail propeller-rotor torque transmissions.
According to the invention comprising the above-mentioned construction, the engine gearbox supplies the cylindrical input shafts with rotational motive power.
The rotation of the input shafts is transmitted simultaneously to the propeller shafts and the rotor shafts by the propeller-rotor torque transmissions. At this point, the propellers and the rotor blades rotate.
During takeoff of the aircraft, the pitch angles (blade angles) of the variable pitch propellers is brought to zero by means of the propeller collective pitch controller, and the collective pitch of the rotor blades is set to a high value.
Under these conditions, the propulsion force due to the propellers becomes zero, and the lift of the rotor blades becomes large. In this case, if the output of the engine gearbox is controlled by the engine power controller such that the rotational speed of the input shafts becomes high, then the aircraft climbs on account of the lift of the rotors while the lift of the fixed wing including the main wing and the horizontal tail wing is zero.
At this point, the aircraft flies in a flight mode wherein the aircraft stays aloft with the fixed wing lift equal to zero (helicopter mode).
If the pitch of the propellers is increased after the aircraft has climbed to the desired altitude, then the aircraft starts to travel forward. The forward flight of the aircraft causes the main wing and the horizontal tail wing to produce lift.
Therefore as the forward travel speed of the aircraft increases, the collective pitch of the rotor blades is decreased. At this point, the lift of the rotors decreases, but the aircraft can fly, since a sufficient lift is provided by the main wing and the horizontal tail wing.
After the lift of the rotors has become zero, the aircraft flies in a flight mode wherein the lift is provided only by the main wing and the horizontal tail wing (fixed wing mode).
In the fixed wing mode, the positions of the control surfaces are controlled to adjust the lift or the air resistance produced during forward flight.
The control surfaces, one of which is provided on each of the right-hand section and the left-hand section of the main wing, the right-hand section and the left-hand section of the horizontal tail wing, and the vertical tail wing serve to adjust the lifts produced by the right-hand section and the left-hand section of the main wing, the right-hand section and the left-hand section of the horizontal tail wing, and the vertical tail wing; and the air resistance produced during forward flight. Thereby making it possible to control the flight direction of the aircraft during forward flight.
In the case of the aircraft of the present invention, the flight mode transition from the helicopter mode to the fixed wing mode can be achieved, unlike the case with conventional aircraft, without performing tilting operation (propeller direction changing operation). Instead, this transition can be made only by changing the collective pitch of the rotor blades and by changing the pitch of the propellers. Therefore the pertinent transition of flight can be achieved safely.
The rotation mechanism and the pitch control mechanism for the rotor blades are simplified, since the rotor blades do not require cyclic control.
The aircraft of the present invention may provide the following advantages
(a) Since vertical takeoff and landing can be made in the helicopter mode, no large airfields are required, thus permitting takeoff from and landing on decks of ships.
(b) High-speed flight can be conducted in the fixed wing mode.
(c) When the load carried by the aircraft is too heavy for vertical takeoff and landing to be made in the helicopter mode, the aircraft may be used as an STOL aircraft.
For the purpose of resolving the above-mentioned problems, an aircraft of the second aspect comprises the components of the above-mentioned first aspect, wherein a number of components of the first aspect are further specified such that:
(a) two the above mentioned propeller-rotor torque transmissions, one of which is located in the right-hand section of the above mentioned airframe, and, the rest of which is located in the left-hand section of the above mentioned airframe; and
(b) a directional (yaw) control system which serves to independently control the pitch angles of each of variable pitch propellers of two the above mentioned propeller-rotor torque transmissions, thereby controlling the flight direction of the above mentioned aircraft.
In the case of the aircraft of the second invention comprising the above-mentioned construction, the directional (yaw) control system serves to controls the flight direction of the aircraft by independently controlling the pitch angles of the two main propellers one of which is located in the right-hand section of the aircraft and the rest of which is located in the left-hand section of the aircraft.
Namely, by bringing the pitch angle of the propeller installed on the right-hand (or left-hand) main propeller-rotor torque transmission to a higher value than the pitch angle of the propeller installed on the left-hand (or right-hand) main propeller-rotor torque transmission, a yawing moment is created on the aircraft, thereby performing directional (yaw) control of the aircraft. This yaw control can also be performed in a flight mode wherein the aircraft has no forward speed (helicopter mode).
For the purpose of resolving the above-mentioned problems, an aircraft of the third aspect comprises the components of the above-mentioned first aspect, wherein a number of components of the first aspect are further specified such that,
a first propeller-rotor torque transmission and a second propeller-rotor torque transmission each of which has a rotor shaft and two propeller shafts rotating at the same speed as the above mentioned rotor shafts are provided.
In the case of the aircraft of the third aspect comprising the above-mentioned construction, the two propellers on the first (or second) propeller-rotor torque transmission can be prevented from colliding with the blades of the rotor on the first (or second) propeller-rotor torque transmission even if the planes of rotation of the propellers on the first (or second) propeller-rotor torque transmission intermesh with the plane of rotation of the rotor on the first (or second) propeller-rotor torque transmission.
For the purpose of resolving the above-mentioned problems, a fourth aspect of the present invention comprises the components of the above-mentioned first aspect, except that:
a bi-blade rotor is used in lieu of the above mentioned rotor having single blades, or a bi-blade variable pitch propeller is used in lieu of the above mentioned variable pitch propeller having a single blade.
In the case of the fourth aspect comprising the above-mentioned construction, wherein bi-blade rotors or bi-blade variable pitch propellers are used, the number of rotor blades or variable pitch propellers can be increased as compared with the case where neither bi-blade rotors nor bi-blade variable pitch propellers are used. Therefore, the radii of rotation of rotor blades or variable pitch propellers can be reduced, thereby permitting the size of the aircraft storage space to be diminished.
A torque transmission of the fifth aspect comprises:
(a) a shaft support coupler whereto the end of each of a first drive shaft supports and a second drive shaft support, both of which lie at right angles to each other, and the end of a third drive shaft support are linked in such a way as to preclude rotation,
(b) a third drive shaft support which lies at right angles to said first and second drive shaft support, or lies coaxially with said first or second drive shaft support, and is located on the other side of said shaft support coupler;
(c) a first drive shaft, a second drive shaft, and a third drive shaft, all of which are cylindrical and are installed around said first through third drive shaft supports, respectively ; and
(d) a torque transmission bevel gear train wherein at least one bevel gear is installed on each of said first through third drive shafts such that the rotation of one of said first through third drive shafts is transmitted simultaneously to the other drive shafts.
In the case of the invention of the torque transmission comprising the above-mentioned construction, if one of the above-mentioned first through third drive shafts is used as an input shaft, and if the other two drive shafts are used as output shafts, then either: both of the output shafts lie at right angles to the input shaft; or one of the output shafts lies at right angles to the input shaft, and the other output shaft is positioned coaxially with the input shaft and is located on the opposite side of the above-mentioned shaft support coupler.
A torque transmission of the sixth aspect comprises the components of the above-mentioned fifth invention, wherein a number of components of the fifth aspect are further specified such that:
a torque transmission bevel gear train wherein
a first small bevel gear and a first large bevel gear are installed on one of said first through third drive shafts;
a second small bevel gear is installed on one of the drive shafts on which neither said first small bevel gear nor said first large bevel gear is installed; and
a second large bevel gear is installed on the drive shaft on which no other drive bevel gear is installed; such that said first small bevel gear and said second small bevel gear mesh with each other; and said first large bevel gear and said second large bevel gear mesh with each other.
In the case of the torque transmission of the sixth aspect comprising the above-mentioned components, one of the above-mentioned first through third drive shafts may be used as an input shaft, and the two other drive shafts may be used as output shafts.
If the numbers of teeth of the bevel gears on the above-mentioned first through third drive shafts are chosen pertinently, then the rotational speeds of the first through third drive shafts can be made different from one another.
A torque transmission of the seventh aspect has three drive shafts all of which lie at right angles to one another.
A torque transmission of the eighth aspect has three drive shafts all of which lie on a plane.
A torque transmission of the ninth aspect differs from the fifth aspect in that:
(c) a fourth drive shaft support which lies coaxially with one of the three drive shafts consisting of said first through third drive shafts and is linked to the opposite side of said shaft support coupler in such a way as to preclude rotation; and
(d) a fourth drive shaft which is installed on said fourth drive shaft support in such a way as to permit rotation and on which is installed a bevel gear that meshes with a bevel gear installed on one of the drive shafts each mounted on one of two drive shaft supports consisting of said three drive shaft supports less the drive shaft support lying with said fourth drive shaft support.
In the case of the torque transmission of the ninth aspect comprising the above-mentioned components, one of the above-mentioned four drive shafts may be used as an input shaft and the three other drive shafts may be used as output shafts.
A torque transmission of the tenth aspect differs from the ninth aspect in that:
(a) a fifth drive shaft support which lies coaxially with one of the four drive shafts consisting of said first through fourth drive shafts and is linked to the opposite side of said shaft support coupler in such a way as to preclude rotation; and
(b) a fifth drive shaft which is installed on said fifth drive shaft support in such a way as to permit rotation and on which is installed a bevel gear that meshes with a bevel gear installed on one of the drive shafts each mounted on one of three drive shaft supports consisting of said four drive shaft supports less the drive shaft support lying coaxially with said fifth drive shaft support.
In the case of the torque transmission of the tenth aspect comprising the above-mentioned components, one of the above-mentioned five drive shafts may be used as an input shaft and the four other drive shafts may be used as output shafts.
A torque transmission of the eleventh aspect differs from the tenth aspect in that:
(a) a sixth drive shaft support which lies coaxially with one of the five drive shafts consisting of said first through fifth drive shafts and is linked to the opposite side of said shaft support coupler in such a way as to preclude rotation; and
(b) a sixth drive shaft which is installed on said sixth drive shaft support in such a way as to permit rotation and on which is installed a bevel gear that meshes with a bevel gear installed on one of the drive shafts each mounted on one of four drive shaft supports consisting of said five drive shaft supports less the drive shaft support lying coaxially with said sixth drive shaft support.
In the case of the torque transmission of the eleventh aspect comprising the above-mentioned components, one of the above-mentioned six drive shafts may be used as an input shaft and the five other drive shafts may be used as output shafts.